The Ongoing Outburst of the Eclipsing Symbiotic Nova AS 296: The First 1200 days

Ultraviolet, optical, and infrared photometry is reported for the symbiotic star AS 296, spanning the first 1200 d of its outburst which began in June 1988. The effects of the outburst were restricted to the wavelength interval 2200-7500 A. The progress of the event was followed through two maxima and two eclipses of the hot source by the M5 III companion. An orbital period of 650 d was derived from the eclipses. At no stage of the ourburst did the luminosity approach the Eddington value, and no material was ejected from the system. The most likely source of the quiescent luminosity of AS 296 is stable hydrogen burning of material accreted from the M giant onto the surface of the white dwarf. It is therefore tentatively suggested that the multiple maxima of the outburst are the consequence of repeated helium shell flashes in this accreted and processed material. It is further suggested that objects such as AS 296 may be the progenitors of type Ia supernovae.